464 SUPPLEMENTARY NOTES* 



weeks, and sulphate of copper added from time to time, the sulphuret 

 of copper formed rather a thick crust immediately under the metallic 

 crystals, and appeared almost black and somewhat friable. He 

 considered that the oxide of copper in the solution parted with its 

 oxygen to a portion of the sulphur of the bi-sulphuret, thus form- 

 ing sulphuric acid, which was transmitted through the clay to the 

 Zinc in the other cell, whilst the de-oxydized copper was deposi- 

 ted on the electro-negative copper ore. These results seemed to 

 explain the reason why metallic copper is found in the mines in 

 contact with the sulphuret and black copper ore, and not with the 

 yellow bi-sulphuret of that metal ; and likewise why the sulphuret 

 of copper commonly occurs in metallic veins nearer the surface 

 than the yellow bi-sulphuret, where it is exposed to the action of 

 water and of ferruginous matter, as indicated by the " gossan,'"' or 

 oxide of Iron, which occurs in the upper regions of Copper mines 

 in Cornwall. Mr. E. W. Fox referred also to his experiments on 

 the electro-magnetic condition of metallic veins, and adduced proofs 

 of the electricity which he had detected in them, being indepen- 

 dent of accidental influence; indeed, he obtained very decided 

 voltaic action when a piece of sulphuret, and another of yellow bi- 

 sulphuret of copper were dipped in water, taken from a mine, the 

 former being electro-positive with respect to the latter. This ex- 

 periment shows that the voltaic action between different metallic 

 lodes, and different parts of the same lode, must be very great. 

 He was induced to commence his electro-magnetic experiments in 

 mines inconsequence of the analogy which he thought he perceived 

 in mineral veins to voltaic combinations. 



In another experiment Mr. R. W. Fox has substituted the sul- 

 phuret or vitreous copper ore for the piece of Zinc in one of the 

 cells, all other circumstances being the same as before described, 

 and in a few weeks the yellow bi-sulphuret of copper in the other 

 cell was covered with a thin coating of the sulphuret of that metal. 

 He has also found that sulphuretted hydrogen is copiously evolved 

 when yellow copper ore is placed in a solution of sulphate of Zinc 

 or of Iron in one of the cells, and connected, by means of a wire, 

 with a piece of Zinc in the water of the other cell. As sulphu- 

 retted hydrogen has the property of precipitating most of the me- 

 tals from their solutions, in the form of sulphurets, this experiment 



